Electrodeposition process using a novel pigment dispersant

ABSTRACT

It has been found that basic nitrogen-containing adducts of glycidyl ethers or esters containing an acyclic hydrocarbon chain of at least eight carbon atoms with secondary amine or a tertiary amine salt are useful as grinding media in preparing stable pigment dispersions useful in water-soluble coating systems, for example, electrodepositable compositions.

United States Patent 1 Jerabek ELECTRODEPOSITION PROCESS USING A NOVELPIGMENT DISPERSANT [75] Inventor: Robert D. Jerabek, Glenshaw, Pa. [73]Assignee: PPG Industries, Inc., Pittsburgh, Pa. [22] Filed: Jan. 3, 1974[21] Appl. No.: 430,450

Related US. Application Data [60] Division of Ser, No. 248,752, April28, 1972, Pat. No. 3,842,l l l, which is a continuatiomin-part of Ser.No. 193,590, Oct. 28, 1971.

[52] US. Cl. 204/181 [Sl] Int. Cl. C25D 13/06; C25D 13/10 [58] Field ofSearch 204/l8l; 106/308 N [56] References Cited UNITED STATES PATENTS3,6l7,458 l 1/1971 Brockman 204/181 Dec. 9, 1975 3.640.926 2/l972 Slateret al 0. 204/[8] Primary ExaminerHoward S. Williams Attorney, Agent, orFirmWil1iam J. Uhl

ABSTRACT 6 Claims, N0 Drawings ELECTRODEPOSITION PROCESS USING A NOVELPIGMENT DISPERSANT CROSS-REFERENCE TO RELATED APPLICATIONS Thisapplication division of copending Application Ser. No. 248,752, filedApr. 28, 1972, now US. Pat. No. 3,842.1 l l, which, in turn, is acontinuation-in-part of Application Ser. No. 193,590, filed Oct. 28,1971.

STATE OF THE ART In the formation of paint compositions and especiallyelectrodepositable paint compositions, an important factor is theintroduction of pigments into the coating composition. Pigments aretypically ground in a dispersing agent and then the resultant pigmentpaste is incorporated into the coating composition to give the coatingcomposition proper color, or opacity and application or film properties.

The time required for grinding some pigments and dispersing of thesepigments poses a problem in some instances. Further, electrodepositablecompositions have been frequently found wherein the resin whichultimately makes up the majority of the vehicle resin present in thecomposition is not suitable as a grinding medium, since the pigmentpaste formed does not have stable properties and upon storage for anylength of time produces a composition which cannot be readily dispersedor which adversely affects the properties of the electrodepositablecomposition ultimately formed.

DESCRIPTION OF THE INVENTION It has now been found that stable pigmentpaste for cationic electrodepositable compositions can be prepared byusing as the dispersing media a basic nitrogen containing adduct of along chain glycidyl ether or ester. This grinding media allows for thepreparation of pigment pastes which are stable and which are compatiblewith cationic electrodepositable vehicle resin compositions based onamine group-containing solubilized electrodepositable resins.

The basic nitrogen-containing adducts utilized to form the pigmentpastes of the instant invention are adducts of fatty acid glycidylethers or esters of a fatty alcohol or acid. By fatty alcohol or acid ismeant an acyclic acid or alcohol containing 8 to 24 carbon atoms.Typical examples of these acids and alcohols include the saturatedstraight chain and branched chain series of fatty alcohols and acids aswell as ethylenically unsaturated species and mixtures thereof,including octanoic or 2-ethyl hexanoic acid at the lower end proceedingto lauric, palmitic, stearic, etc., at the upper end of the group.Highly-branched tertiary carboxylic acid mixtures such as Shell'sVersatic 91 1 acids are also useful. Fatty alcohols of equivalent chainlength are used for the preparation of the glycidyl ethers.

The glycidyl ethers or esters are well noted in the art and in somecases are items of commerce and their preparation need not be discussedin detail. Particularly useful are Proctor and Gambles Epoxide 7 toEpoxide 45 Series of glycidyl ethers as well as Shell Chemical CompanysCardura E glycidyl ester.

The basic nitrogen-containing adduct is prepared by reacting theglycidyl compound with a secondary amine or a tertiary amine salt. Thesecondary amine may be any water-soluble secondary amine, includingalkyl amines and alkanolamines. Also useful is a diketi- 2 mine having afree secondary amine group, for example, the diketimine derived from onemole of diethylenetriamine and two moles of methylisobutyl ketone(Shells curing agent H-l which reacts through the free amine group. Whenthe product of this reaction is contacted with water, the ketiminegroups are hydrolyzed, forming free primary amine groups in addition tothe tertiary amine group formed in the initial reaction.

The tertiary amine salts may be any water-soluble tertiary amine salt,and is preferably a salt of an acid having a dissociation constantgreater than l X 10' and. most preferably, is an organic acid. Suitableacids include boric acid, hydrochloric acid, phosphoric and sulfuricacid, lactic acid, acetic acid, propionic acid and butyric acid.

The amines from which the salts are formed include any unsubstitutedorganic amine or amine substituted with non-reactive substituents, suchas halogen or hydroxyl amines. Specific amines include triethylamine,dimethylethanolamine trimethylamine and the like. The presentlypreferred amine salt is dimethylethanolamine lactate.

The basic nitrogen-containing adduct is prepared by reacting theglycidyl ether or ester with the secondary amine or tertiary amine saltin approximately a 1:1 mole ratio. The reaction proceeds at roomtemperature in most cases and in some instances exothermically so thatmoderate cooling may be necessary. In some cases moderately elevatedtemperatures are preferred. Typically, the reaction is conducted betweenabout 50C. and about C. The reaction may be conducted in the presence ofa solvent if desired. If a solvent is employed, preferably it iscompatible and useful in the ultimate composition which is formed. Forexample, alcohols, ketones and glycol ethers may be used.

The resultant adduct is preferably insoluble in water unless solubilizedwith an acid.

The novel pigment dispersant of the invention comprises theabove-described adduct or a solution thereof, which is at leastpartially neutralized with a water-soluble acid such as isconventionally employed in solubilizing cationic water-based, andparticularly electrodepositable, compositions. Sufficient acid isusually employed to prepare an aqueous dispersion and this usuallycomprises at least about 50 percent theoretical neutralization.

The pigment pastes of the invention are prepared by grinding ordispersing a pigment in the presence of a pigment dispersant in a mannerwell known in the art.

The pigment paste comprises as essential ingredient the dispersant andat least one pigment; however, the paste may, in addition, contain otheradjuvants such as plasticizers and the like, or wetting agents,surfactants or defoamers.

The pigment dispersant is employed in a vehicle to prepare a pigmentpaste in the manner well known in the art.

Generally and preferably the pigment paste is prepared in the presenceof water and in that case contains in general at least about 50 percentwater, although less can be employed and, in fact, the pigmentdispersant of the invention can be utilized to prepare non-aqueouspigment pastes which are subsequently dispersible in water-basedcompositions.

Any of the conventional pigments employed in water-based andparticularly electrodeposition compositions may be dispersed in theabove-described dispersants.

The pigment and dispersant may be ground in the conventional manner suchas in a steel ball mill, attritor, or sand mill.

The pigment and dispersant ratios vary from pigment to pigment over awide range, usually from about two percent to about 50 percent by weightof dispersant, based on pigment weight, may be used.

The final electrodepositable composition may contain, in addition to thepigment dispersion and acid solubilized amine group-containing resin,crosslinking resins, solvents, antioxidants, surfactants and otheradjuvants typically employed in the electrodepositable composition.

A number of amine group-containing, acid-solubilized, cationicelectrodepositable resins are known in the art and need not be describedin detail. Virtually any polyamine group-containing resin which can beacid-solubilized may be employed as an aqueous coat ing composition.Preferably the resin also contains hydroxyl groups. These resins includemulticomponent resin systems which contain two essential components, forexample, a polyamine group-containing resin together with a fully cappedorganic polyisocyanate described in copending Application Ser. No.47,917, filed June 19, 1970, now US. Pat. No. 3,799,854 and Ser. No.193,590, filed Oct. 28, 1971, which are hereby incorporated byreference; as well as in systems containing an essentially self-curingresin system, for example, resin containing amine groups, hydroxylgroups and capped isocyanate groups within the same molecule, where thecapped isocyanate groups are stable at room temperature in the presenceof hydroxyl or amine groups but reactive with hydroxyl groups atelevated temperatures. Preferably, the isocyanate groups are capped withan aliphatic alkyl, alkoxyalkyl, cycloaliphatic alkyl, or aromatic alkylmonoalcohol or an oxime. Preferably, the resin contains about 0.5 toabout 2.0 latent isocyanate groups per hydroxyl group. Resins withinthis class are described in copending Application Ser. No. 193,591,filed Oct. 28, 1971 and Ser. No. 203,875, filed Dec. 1, 197 1, which arehereby incorporated by reference.

Enough pigment paste is used to that the final electrodepositablecomposition has the desirable properties. In most instances, the finalelectrodepositable composition has a pigment-to-binder ratio of betweenabout 0.05 to about 0.5.

In electrodeposition processes employing the aqueous coatingcompositions described above, the aqueous composition is placed incontact with an electricallyconductive anode and anelectrically-conductive cathode in an electric circuit. While in contactwith the bath containing the coating composition, an adherent film ofthe coating composition is deposited on the cathode. This is in contrastto processes utilizing polycarboxylic acid resins which deposit on theanode, and many of the advantages described above are in large partattributed to this cathodic deposition.

The conditions under which the electrodeposition is carried out are, ingeneral, similar to those used in electrodeposition of other types ofcoatings. The applied voltage may be varied greatly and can be, forexample, as low as one volt or as high as several thousand volts,although typically between 50 volts and 500 volts. The current densityis usually between about 1.0 ampere and amperes per square foot, andtens to decrease during electrodeposition.

The method of the invention is applicable to the coating of anyelectrically-conductive substrate, and especially metals such as steel,aluminum, copper or the like.

After deposition, the coating is cured at elevated temperatures by anyconvenient method such as in baking ovens or with banks of infrared heatlamps.

Illustrating the invention are the following examples, which are not tobe construed as limiting the invention to their details. All parts andpercentages in the examples, as well as throughout this specification,are by weight unless otherwise specified.

EXAMPLE I A cationic pigment dispersant was prepared by heating 746.2parts of stearyl glycidyl ether (Proctor and Gambles Epoxide 45) and 224parts of ethylene glycol monobutyl ether to about 50C. and adding 150.2parts of n-methyl ethanolamine over a 30-minute period with externalcooling to keep the batch temperature below 100C. When all the amine wasadded, the batch was held an additional hour at 100C. before cooling andstorage.

To prepare a grinding vehicle from this cationic pigment dispersant, 200parts were blended with 39.5 parts of 88 percent lactic acid and 515parts of deionized water.

To prepare a pigment paste, 90 parts of this grinding vehicle wasblended with four parts of acetylenic alcohol defoamer (Surfynol 104-A),60 parts of phthalocyanine blue, 140 parts of iron oxide brown and 306parts of deionized water, and the resultant slurry ground in a suitablemill to a Hegman No. 7.

EXAMPLE 11 An amine-epoxy adduct was prepared as follows:

One thousand eight hundred thirty parts of polyglycidyl ether ofbisphenol A (Epon 1004) possessing an epoxy equivalent weight of 915were dissolved in 35 3.2 parts of methyl butyl ketone by heating toreflux at 130C. with agitation in order to remove any water present byuse of a decanting trap in the distillate return line. Upon cooling to80C. under a dry nitrogen blanket, 52 parts of the diketimine derivedfrom one mole of diethylene triamine and 2 moles of methyl isobutylketone (as described in US. Pat. No. 3,523,925) and 138.8 partsdiethylamine were added and the batch heated to 120C, where it was heldapproximately 2 hours and then thinned with 326 parts of propyleneglycol monomethyl ether. The resultant polytertiary amine cationic resincontaining potential primary amine groups (to be generated from theketimine moiety upon water addition) was stored for subsequent use. Thisproduct was identified as Adduct C.

1n order to prepare a reactive cationic plasticizer, the 2-ethylhexanolmonourethane of 2,4-toluene diisocyanate was first prepared by adding1953 parts of 2-ethylhexanol to 2610 parts of 2,4-toluene diisocyanateand 200 parts methyl butyl ketone over a 5-hour period with agitationand external cooling to maintain the batch reaction temperature below20C. The batch was then thinned with parts of methyl butyl ketone andstored under dry nitrogen.

In another reactor, 456 parts of the above Z-ethylhexanol monourethaneof 2,4-TD1 (1.5 equivalents of free isocyanate) was added to 7695 parts(1.5 equivalents) of polyoxypropylene diamine (Jeffersons .leffamineD-1000) possessing an amine equivalent weight of 512 over a 20-minuteperiod at 40C., and then thinned with 189 parts of methyl butyl ketoneto yield a reactive cationic plasticizer of 85.2 percent nonvolatilecontent.

ln another reactor, the 2-ethylhexanol diurethane of 80/202,4/2,6-toluene diisocyanate was prepared by slowly adding 87.1 parts of80/20 2,4/2,6-TD1 to 143 parts of 2-ethy1hexanol containing one drop ofdibutyl tin dilaurate with external cooling to maintain the reactionmixture below 100C.

To prepare an electrodepositable thermosetting cationic urethanecomposition, 741 parts of the above polytertiary amine cationic resin(Adduct C), 57 parts of ethylene glycol monohexyl ether, 134 parts ofthe above reactive cationic plasticizer, 231 parts of the aboveZ-ethylhexanol diurethane and 18 parts dibutyl tin dilaurate catalystwere blended and then solubilized with 46 parts of 88 percent lacticacid and 1773 parts deionized water.

To pigment this composition, 1216 parts of it were blended with 247parts of the pigment paste described in Example 1, and the batch thinnedto about 12 percent non-volatile content with 2337 parts of deionizedwater.

This electrodeposition bath showed a pH of 6.0 and 2 minute throwpowerof inches at 280 volts. Films deposited cathodically for two minutes at280 volts on zinc phosphated steel and baked 45 minutes at 350F. yieldedsmooth, hard, flexible films of 0.5 mil thickness.

EXAMPLE III A 2-ethylhexanol monourethane of 2,4-toluene diisocyanatewas prepared by adding 585.9 parts of 2-ethy1- hexanol to an agitatedmixture of 793 parts of 2,4-toluene diisocyanate and 60 parts of methylbutyl ketone over approximately a 5-hour period with external cooling tomaintain the reaction temperature below 30C. After the addition wascomplete, an additional 30 parts of methyl butyl ketone was added; andthe batch stored under dry nitrogen for subsequent use.

A self'crosslinking cationic polyurethane resin was then prepared byfirst dissolving 632.4 parts of polyglycidyl ether of bisphenol A (Epon1001) possessing an equivalent weight of 526 per epoxide group, in 177.4parts of methyl butyl ketone, and refluxing for about 15 minutes toremove any water present by use of a decanting trap in the distillatereturn line. After cooling to 70C., 87.7 parts of diethylamine wereintroduced and the batch heated to about 140C. with removal of about 100parts of solvent. The batch was then cooled to 100C., the solventreplaced, and 522.4 parts of the above 2-ethylhexanol monourethane of2,4-to1uene diisocyanate added. Upon heating the batch to 120C, over aone-hour period, all NCO was found to have reacted, as indicated by aninfrared scan. The batch was then thinned to 78 percent solids with 196parts of propylene glycol monomethyl ether.

A reactive plasticizer for use with this self-crosslinking cationicurethane resin was then prepared by adding 248 parts of the2-ethylhexanol monourethane of 2,4toluene diisocyanate to 1250 parts ofpolytetramethylene glycol (Quaker Oats POLYMEG 3000) possessing anaverage molecular weight of 2940 and heating the mixture to lO0-ll0C.and holding for about 5 hours until all NCO groups were reacted, asdetermined by infra-red scanning.

To 487 parts of the above cationic urethane was blended 43 parts of theabove reactive plasticizer, and 38 parts ethylene glycol monohexylether. This mixture was neutralized with 39 parts 88 percent lacticacid, then blended with 8 parts dibutyl tin dilaurate, 215 parts of thepigment paste of Example I and, finally, thinned with 3465 parts ofdeionized water. This pigmented self-crosslinking polyurethane cationicelectrodepositable composition of approximately 12 percent solids showeda pH of 4.5, conductivity of 875 mmhos./cm., and 2-minute Ford throwpower of 7-3/8 inches at 350 volts.

When cathodically deposited upon an untreated cold-rolled steel panelfor 2 minutes at 350 volts, and

" cured 45 minutes at 350F., this composition yielded a smooth film of0.3 mil thickness and 3H pencil hardness, which when scribed and placedin a salt fog cabinet at F. for 14 days displayed little or no rustcreepage at the scribe.

EXAMPLE IV A Z-ethylhexanol monourethane of 2,4-toluene diisocyanate wasprepared by adding 1953 parts of 2-ethylhexanol to an agitated mixtureof 2610 parts of 2,4-TD1 and 200 parts of methyl butyl ketone overapproximately a three-hour period with external cooling to maintain thereaction temperature below 18C. After the addition was completed, theproduct was stored under dry nitrogen for subsequent use.

A self-crosslinking cationic polyurethane-containing free primary aminegroups was prepared by first dissolving 700 parts of polyglycidyl etherof Bisphenol A (Epon l00l) possessing an equivalent weight of 492 perepoxide group, in 150 parts of methylbutyl ketone, and refluxing about30 minutes at 130C. to remove any water present by use of a decantingtrap in the distillate return line. After cooling to 100C, 598.3 partsof the above 2-ethy1hexano1 monourethane of 2,4-to1- uene diisocyanatewas added, along with ten drops of dibutyl tin dilaurate.

The batch was heated to 120C. and held about 35 minutes, at which time143.2 parts of ethylene glycol monohexyl ether was added, followed by96.1 parts of n-methyl ethanolamine and 73.8 parts of the diketiminederived from one mole of diethylene triamine and 2 moles ofmethylisobutyl ketone (Shell Chemical Companys curing agent H-l). Thebatch was held at 100C. for about 2 hours, at which time 1400 parts ofit were poured into an agitated vessel containing 831 parts of deionizedwater and 72 parts of 88 percent lactic acid. After cooling to F., 23parts of dibutyl tin dilaurate were added to the mixture and it wasthinned for subsequent use to 40 percent non-volatile content with 582parts of deionized water.

A cationic pigment dispersant was prepared by he ating 746.2 parts ofstearyl glycidyl ether (Proctor and Gambles Epoxide 45) and 224 parts ofethylene glycol monobutyl ether to about 50C. and adding 150.2 parts ofn-methyl ethanolamine over a 30 minute period with external cooling tokeep the batch temperature below 100C. When all the amine was added, thebatch was held an additional hour at 100C. before cooling an storage. Toprepare a grinding vehicle from this cationic pigment dispersant, 200parts were blended with 38.5 parts of 88 percent lactic acid and 515parts of deionized water. To prepare a pigment paste 90 parts of thisgrinding vehicle were blended with 4 parts of acetylenic alcoholdefoamer (Surfynol l04-A), 60 parts of 7 phthalocyanine blue, 140 partsof iron oxide brown and 306 parts of deionized water, and the resultantslurry ground in a steel ball mill.

A pigmented, self-crosslinking cationic, primary amine-containing,electrodepositable composition was prepared by blending 228 parts of theabove paste with 930 parts of the above 40 percent non-volatile cationicresin dispersion and reducing with 2642 parts of deionized water. Thiscoating bath showed a pH of 6.4, a conductivity of l l0 mmhos./cm., anda 2-minute throw power (Ford) of 8-:2 inches at 250 volts.

Films deposited cathodically for two minutes at 250 volts on zincphosphated steel panels showed 0.4 mil film thickness after curingminutes at 400F. and showed no scribe creepage when exposed to salt fogat lOOF. for 2 weeks.

In a manner similar to that specifically described, various otheradducts can be prepared using various glycidyl compounds and aminecompounds within the disclosure above. Likewise, other pigments andelectrodepositable resins may be employed to achieve similar results.

According to the provisions of the Patent Statutes, there are describedabove the invention and what are now considered to be its bestembodiments; however, within the scope of the appended claims, it is tobe understood that the invention can be practiced otherwise than asspecifically described.

I claim:

l. A method of electrocoating an electrically-conductive surface servingas a cathode in an electrical circuit comprising said cathode, an anodeand an aqueous electrodepositable composition wherein theelectrodepositable composition comprises an aqueous dispersion of:

A. an acid-solubilized polyamine group-containing resin and B. a pigmentpaste comprising 1. an adduct comprising the reaction product of:

a. a fatty glycidyl ether or ester; and b. a secondary amine or tertiaryamine salt; said adduct being at least partially neutralized with awater-soluble acid; and 2. a pigment dispersed therewith.

2. A method as in claim 1 wherein (a) is a fatty glycidyl ether.

3. A method as in claim 2 wherein (b) is a lower alkyl or alkanolsubstituted secondary amine.

4. A method as in claim 1 wherein (A) is an acidsolubilized,self-curing, synthetic organic resin containing amino groups, hydroxylgroups and capped isocyanate groups stable at room temperature in thepresence of hydroxyl or amino groups and reactive with hydroxyl groupsat elevated temperatures.

5. A method as in claim 4 wherein (a) is a fatty glycidyl ether.

6. A method as in claim 4 wherein (b) is a lower alkyl or alkanolsubstituted secondary amine.

L H Hui) 3i Ahab PAIL. 1 UK 5* 1' CERTIFICATE OF CORRLCIIUN PULNTNU3,925,180

UK I b December 9, 1975 INVL N iURr Robert D. Jerabek It i certrfiedthat error appears In the ab0ve-identrfied patent and that said LettersPatent vn9 herrahy .5 shown below,

Under "Related U.S. Application Data" on the cover page, Patent No."3,842,111" should be -3,824,lll-- Column 1, line 9, "3,842,111" shouldbe -3,824,1ll.

Signed and Scaled this thirtieth Day of March 1976 [SEAL] Arrest:

RUTH C. Mei-SON C. MARSHALL DANN K 11" Commissioner nflarenrs andTrademarks

1. A METHOD OF ELECTROCOATING AN ELECTRICALLY-CONDUCTIVE SURFACE SERVINGAS A CATHODE IN AN ELECTRICAL CIRCUIT COMPRISING SAID CATHODE, AN ANODEAND AN AQUEOUS ELECTRODEPOSITABLE COMPOSITION WHEREIN THEELECTRODEPOSITABLLE COMPOSITION COMPRISES AN AQUEOUS DISPERSION OF: A.AN ACID-SOLUBILIZED POLYAMINE GROUP-CONTAINING RESIN AND B. A PIGMENTPASTE COMPRISING
 1. AN ADDUCT COMPRISING THE REACTION PRODUCT OF: A. AFATTY GLYCIDYL ETHER OR ESTER; AND B. A SECONDARY AMINE OR TERTIARYAMINE SALT; SAID ADDUCT BEING AT LEAST PARTIALLY NEUTRALIZED WITH AWATER-SOLUBLE ACID; AND
 2. A PIGMENT DISPERSED THEREWITH.
 2. a pigmentdispersed therewith.
 2. A method as in claim 1 wherein (a) is a fattyglycidyl ether.
 3. A method as in claim 2 wherein (b) is a lower alkylor alkanol substituted secondary amine.
 4. A method as in claim 1wherein (A) is an acid-solubilized, self-curing, synthetic organic resincontaining amino groups, hydroxyl groups and capped isocyanate groupsstable at room temperature in the presence of hydroxyl or amino groupsand reactive with hydroxyl groups at elevated temperatures.
 5. A methodas in claim 4 wherein (a) is a fatty glycidyl ether.
 6. A method as inclaim 4 wherein (b) is a lower alkyl or alkanol substituted secondaryamine.